Billed as a collaborative exhibition, this Judy Pfaff double-whammy at 531 West 26 Street reveals an understated bifurcation in Pfaff’s studio production: extroverted and introverted. It also leaves the viewer convinced that, given the opportunity, the artist could have hung new work on every wall in the entire building, and the neighboring addresses as well. She is unstoppable, having devised a working method that is capable of absorbing an enormous range of materials, processes and moods.

At Loretta Howard, Pfaff delivers her familiar but always engaging blend of elegance and ebullience in 14 works of widely varying size, all dated 2014. In smallish works dedicated to Larry Poons, Helen Frankenthaler, Bridget Riley and Jules Olitski, Pfaff tips her hat to movers in mid-20th-century abstraction. In these pieces, shards of colored plastic, deformed by being melted, tangle with acrylic, resin, and pigmented expanded foam, and evoke the formal means of each honoree. The biggest of the tributes is Blue Note (for Al), in which Pfaff’s former teacher, Al Held, is celebrated — a 9-by-14-foot wall work featuring concentric circles of blue and orange Plexiglas, fluorescent lights and a meandering, steel-rod musical staff.

Even more convincing is the gallery’s second space, in which the visitor encounters the two largest works in the show. Pfaff’s use of foam in the (mostly) free-standing, three-part There is a Field, I Will Meet You There (Rumi) recalls Lynda Benglis’s innovative use of similar materials, but whereas Benglis’s roiling mounds of polyurethane feel volcanic, Pfaff’s oozing pools are more like quicksand — once you start to get sucked in, it’s difficult to extricate yourself.

In Alberta, another dimensions-variable work, there are echoes of Frank Stella’s late-1980s and early-90s wall works — those with the relatively restrained palette and the rippling, swirling, organic shapes between which you can see through to the wall. In this company, an untitled work dominated by green plastic is both compact and explosive. To achieve such balance of intimacy and theatricality requires that Pfaff nail the scale of the works relative to the room — and that she does.

The mood is darker at Pavel Zoubok, the work there less immediately ingratiating. Their materials feel clotted rather than clustered — not just layered, but laminated. The checklist runs to 73 items (nearly all from 2014 or 2013), of which many are small, individually framed works, many riffing on botanical and decorative motifs, in encaustic and collage on repurposed ledger paper from India and antique bills of lading from a New York paint company. Across tiled expanses of snapshots and postcards of flora, fauna and her own studio activity, these framed works are arrayed, underscoring the idea of inventory or archive. Wrapping around three walls in the gallery’s back space is one such environment, which includes 21 paper works and an untitled, tendrilly sculpture; the viewer might feel a bit lost in the underbrush. Even more than usual for Pfaff, this installation device risks inelegance for the sake of sheer abundance, as if to assert that the irreducible essence of her practice is proliferation itself.

Among the many sculptural works at Pavel Zoubok, of particular interest is Hydroza, nearly eight feet high and dated 1994-2014. A rough bundle of tar, resin and steel wire, enclosing a big bulb of greenish blown glass, dangles by steel-rod vines from a sort of boom mounted at a perpendicular to the wall. It looks like a nest. The gallery’s overgrown, jungly feeling owes much to the preponderance of materials that have been scavenged from the natural world: Hanging Judge, a walk-through sculpture just inside the entrance, makes effective use of several charred chunks of driftwood; in other works one finds tree branches, dried leaves, deer antlers and sections of honeycomb.

These are combined with repurposed manufactured objects such as paper Chinese lanterns, welded steel furniture, plastic flowers and (naturally) more expanded foam. Twenty-four feet long, Let Sixteen Cowboys Sing Me a Song is anchored by a stringy, undulating frieze of what appears to be seaweed encased in clear resin, an element that plays nicely against the other flotsam washed up in this piece: photographs of giant crustaceans; a translucent pool of pigmented resin, mounted to the wall at looking-glass height; roots, branches, leaves; pinwheeling globs of some unidentified polymer product; photographs of old color engravings of deep-sea fish. A rigid, right-angled, polished steel armature lends visual as much as structural cohesion to this sprawling work.

In the best sense of the term, Pfaff is an artist of the old school. She puts the stamp of her personality on whatever theme she takes up. She thoroughly reinvigorates a tired trope — the natural vs. the man-made — and in the process suggests that just about anything is open to being revisited, reinvented, rediscovered. Embracing a familiar idea and completely recasting it in her own idiom, she demonstrates an awe-inspiring tenacity. To rework an old joke: How do you get to have a two-gallery show in Chelsea? Practice, practice, practice.